The redevelopment of a redundant 1930’s Electricity Sub Station in a Conservation Area provides 21 residential units. The site was defined by the external walls, a deep plan, few windows and no outside spaces. The modulation of the front facade, the addition of windows into the massive side facade, the replacement of the rear facade and the stepping of the plan and section, each move has opened the internal spaces to good daylight and generous terraces and balconies. Five new floors have been constructed with floor to ceiling heights dictated by the principal existing window openings.